1. Field of the Invention
The present invention relates to a pickup system in an optical information recording and reproducing apparatus.
2. Background Art
Generally, a disk which is used as an information recording medium, such as a video disk, a digital audio disk, or the like, is recorded with information signals by means of the formation of fine pits or grooves in spiral tracks on its surface corresponding to the information signals. In the case where the thus recorded information signals are read, the disk is rotated and the tracks are irradiated with a fine spotlight so that the changes of reflected light owing to the presence or absence of the pits are converted into electric signals to thereby reproduce the original information signals from the electric signals.
This reproduction requires that the spotlight be exactly focused on the recording surface of the disk. Accordingly, it is necessary to perform position control by a focusing servo system for an objective lens, which is moved in the direction of the optical axis of the objective lens in order to focus the spotlight on the recording surface. Furthermore, this reproduction requires that the spotlight exactly track the recording tracks. Accordingly, it is necessary to perform additional position control (by a tracking servo system) which moves the spotlight in the direction of the radius of the disk.
For the purpose of performing such position control for the objective lens, a pickup system as shown in FIG. 10 has been conventionally developed.
Referring to FIG. 10, an objective lens 101 is mounted onto the upper end of a cylindrical lens holder 102. The lens holder 102 is mounted onto a base member 106 through two pairs of leaf springs 103 and 104 (that is, four leaf springs) which are unidirectionally flexible in respective directions. A junction member 105 is interposed between the pairs of springs 103 and 104. The lens holder 102, the leaf springs 103 and 104, the junction member 105, the base member 106, and so on make up a supporting mechanism which is arranged to support the objective lens 101 and which enable the objective lens to be moved in the direction of the optical axis of the objective lens (that is, in the direction of the arrow F) and in the direction perpendicular thereto (that is, in the direction of the arrow T). They also align the optical axis of the objective lens 102 to be perpendicular to the recording surface of the disk which is a recording medium.
The lower end of the lens holder 102 forms a round bobbin 102a on which a focusing coil 107 is wound. The round bobbin 102a including the focusing coil 107 is inserted into a cylindrical magnetic circuit 109. A pair of square bobbins 102b extending mutually opposed in the direction of the arrow T are provided at the outer circumference of the lens holder 102 and are integral with the body of the lens holder 102. A tracking coil 110 is wound on each of the square bobbins 102b. The respective square bobbin 102b including the tracking coil 110 is disposed in a magnetic gap formed in a magnetic circuit not shown. By energizing the focusing and tracking coils 107 and 110 with a suitable electric current, the objective lens 101 can be driven in the directions of the arrow F and T.
The pickup system having the above-described construction further has a printed circuit substrate for supplying a driving electric current for the focusing and tracking coils 107 and 110. The printed circuit substrate is mounted on the base member 106. The focusing and tracking coils 107 and 110 are connected to the printed circuit substrate through lead wires. However, the lead wires cften resonate with respect to a driving frequency of the cbjective lens 101 to thereby break the lead wires.